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Kelty-Stephen DG, Lee J, Cole KR, Shields RK, Mangalam M. Multifractal Nonlinearity Moderates Feedforward and Feedback Responses to Suprapostural Perturbations. Percept Mot Skills 2023; 130:622-657. [PMID: 36600493 DOI: 10.1177/00315125221149147] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
An adaptive response to unexpected perturbations requires near-term and long-term adjustments over time. We used multifractal analysis to test how nonlinear interactions across timescales might support an adaptive response following an unpredictable perturbation. We reanalyzed torque data from 44 young and 24 older adults who performed a single-leg squat task challenged by an unexpected mechanical perturbation and a secondary visual-cognitive task. We report three findings: (a) multifractal nonlinearity interacted with pre-perturbation torque production and task error to presage greater pre-voluntary feedforward increases and greater voluntary reductions, respectively, in post-perturbation task error; (b) multifractal nonlinearity presaged relatively smaller task error than standard deviations of both pre-perturbation torques and pre-perturbation task error; and (c) increased task demand (e.g., age-related changes in dexterity and dual-task settings) led to multifractal nonlinearity presaging reduced task error. All these results were consistent with our expectations, except that a pre-perturbation knee torque-dependent increase in post-perturbation task error appeared later for older than for younger participants. This correlational multifractal modeling offered theoretical clarity on the possible roles of nonlinear interactions across timescales, moderating both feedforward and feedback processes, and presaging greater stability when the standard deviation is relatively large and task demands are strong. Thus, multifractal nonlinearity usefully describes movement variability even when paired with classical descriptors like the standard deviation. We discuss potential insights from these findings for understanding suprapostural dexterity and developing rehabilitative interventions.
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Affiliation(s)
- Damian G Kelty-Stephen
- Department of Psychology, 14821State University of New York at New Paltz, New Paltz, NY, USA
| | - Jinhyun Lee
- Department of Physical Therapy and Rehabilitation Sciences, 573932University of Iowa, Iowa City, IA, USA
| | - Keith R Cole
- Department of Health, Human Function, and Rehabilitation Science, 50430George Washington University, Washington, DC, USA
| | - Richard K Shields
- Department of Physical Therapy and Rehabilitation Sciences, 573932University of Iowa, Iowa City, IA, USA
| | - Madhur Mangalam
- Division of Biomechanics and Research Development, Department of Biomechanics, and Center for Research in Human Movement Variability, 14720University of Nebraska at Omaha, Omaha, NE, USA
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2
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Magaldino CM, Amazeen EL. Heavy-tailed distributions in haptic perception of wielded rods. Exp Brain Res 2021; 239:2331-2343. [PMID: 34100097 DOI: 10.1007/s00221-021-06131-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2021] [Accepted: 04/30/2021] [Indexed: 11/30/2022]
Abstract
Humans identify properties (e.g., the length or weight) of objects through touch using somatosensory perceptions in the limbs. Humans identify these properties by manipulating an object to access its inertial qualities. However, there is little work evidencing a unifying pattern of movements humans use to access these inertial properties. The current study examined if participants' wielding movements followed a systematic distribution-specifically, a Lévy-like distribution that is characterized by heavy-tails and is often seen in efficient foraging behavior. Participants wielded rods they could not see and were tasked to identify whether the rod they were wielding was the longer or shorter of two rods. While participants wielded the rod, the rod's motion was captured. Results demonstrate that the sampling of angular accelerations produced heavy-tailed distributions. Since angular acceleration has a distinct physical-mathematical relationship with inertia, this finding is consistent with the interpretation that the haptic subsystems are sensitive to the inertial properties of an object. Angular acceleration from wielding motions appear to follow a similar distribution as optimal foraging strategies-perhaps it is the case that humans are foraging for information about the inertia of an object through changes in angular acceleration and wielding movements.
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Affiliation(s)
| | - Eric L Amazeen
- Department of Psychology, Arizona State University, Tempe, AZ, USA
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3
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Kelty-Stephen DG, Lee IC, Carver NS, Newell KM, Mangalam M. Multifractal roots of suprapostural dexterity. Hum Mov Sci 2021; 76:102771. [PMID: 33601240 DOI: 10.1016/j.humov.2021.102771] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2020] [Revised: 02/01/2021] [Accepted: 02/02/2021] [Indexed: 12/14/2022]
Abstract
Visually guided postural control emerges in response to task constraints. Task constraints generate physiological fluctuations that foster the exploration of available sensory information at many scales. Temporally correlated fluctuations quantified using fractal and multifractal metrics have been shown to carry perceptual information across the body. The risk of temporally correlated fluctuations is that stable sway appears to depend on a healthy balance of standard deviation (SD): too much or too little SD entails destabilization of posture. This study presses on the visual guidance of posture by prompting participants to quietly stand and fixate at distances within, less than, and beyond comfortable viewing distance. Manipulations of the visual precision demands associated with fixating nearer and farther than comfortable viewing distance reveals an adaptive relationship between SD and temporal correlations in postural fluctuations. Changing the viewing distance of the fixation target shows that increases in temporal correlations and SD predict subsequent reductions in each other. These findings indicate that the balance of SD within stable bounds may depend on a tendency for temporal correlations to self-correct across time. Notably, these relationships became stronger with greater distance from the most comfortable viewing and reaching distance, suggesting that this self-correcting relationship allows the visual layout to press the postural system into a poise for engaging with objects and events. Incorporating multifractal analysis showed that all effects attributable to monofractal evidence were better attributed to multifractal evidence of nonlinear interactions across scales. These results offer a glimpse of how current nonlinear dynamical models of self-correction may play out in biological goal-oriented behavior. We interpret these findings as part of the growing evidence that multifractal nonlinearity is a modeling strategy that resonates strongly with ecological-psychological approaches to perception and action.
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Affiliation(s)
| | - I Chieh Lee
- UNC-NC State Joint Department of Biomedical Engineering, UNC-Chapel Hill, Chapel Hill, NC 27514, USA
| | - Nicole S Carver
- Department of Psychology, University of Cincinnati, Cincinnati, OH, United States
| | - Karl M Newell
- Department of Kinesiology, University of Georgia, Athens, GA 30602, USA
| | - Madhur Mangalam
- Department of Physical Therapy, Movement and Rehabilitation Sciences, Northeastern University, Boston, MA 02115, USA.
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Porto C, Lemos T, Sá Ferreira A. Reliability and robustness of optimization properties for stabilization of the upright stance as determined using posturography. J Biomech 2020; 103:109686. [PMID: 32139097 DOI: 10.1016/j.jbiomech.2020.109686] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2019] [Revised: 02/21/2020] [Accepted: 02/23/2020] [Indexed: 11/27/2022]
Abstract
Diagnostic value of static posturography depends on its methodological features, measurement properties, and on computational methods that extract meaningful information from the postural sway i.e. the center-of-pressure (CoP) displacements. In this study, we assessed the reliability and robustness of the postural system based on the optimization properties of the CoP signal: descending, local and global stability, and convergence. For the analysis, we used CoP data from 146 participants (104 [71%] female, age 46 ± 23 years, body mass index 23.6 ± 3.4 kg/m2) recorded while standing quietly on a foam surface without visual input. Reliability was estimated using the intraclass correlation coefficient from a single (ICC2,1) and averaged (ICC2,3) measurements. Robustness was assessed through main and interaction effects for the signal duration (60, 30 s), sampling frequency (100, 50 Hz), and lowpass filtering cutoff frequency (10, 5 Hz). The observed reliability depended on the use of average or single measurements as it was excellent for the stability property (ICC2,k ≥ 0.772); excellent-to-acceptable (ICC2,3 ≥ 0.540) or excellent-to-unacceptable (ICC2,1 ≥ 0.281) for the descending property; and excellent-to-unacceptable (ICC2,3 > 0.295; ICC2,1 > 0.122) for the convergence property. Robustness analysis showed large main effects of signal duration (ω2 ≤ 0.834, p < 0.001), sampling frequency (ω2 ≤ 0.526, p < 0.001), and the lowpass filter cutoff frequency (ω2 ≤ 0.523, p < 0.001) on the optimization properties; but all two-way and three-way effects varied from medium to trivial. Reliability is thus excellent to acceptable for deriving the descending, stability, and convergence properties from the average of three measurements. Those optimization properties are robust to the interaction but not the main effects of methodological sources of variation of posturography.
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Affiliation(s)
- Carla Porto
- Laboratory of Computational Simulation and Modeling in Rehabilitation, Postgraduate Program of Rehabilitation Sciences, Centro Universitário Augusto Motta/UNISUAM, Rio de Janeiro, RJ, Brazil
| | - Thiago Lemos
- Laboratory of Computational Simulation and Modeling in Rehabilitation, Postgraduate Program of Rehabilitation Sciences, Centro Universitário Augusto Motta/UNISUAM, Rio de Janeiro, RJ, Brazil
| | - Arthur Sá Ferreira
- Laboratory of Computational Simulation and Modeling in Rehabilitation, Postgraduate Program of Rehabilitation Sciences, Centro Universitário Augusto Motta/UNISUAM, Rio de Janeiro, RJ, Brazil.
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Zwaferink JBJ, Hijmans JM, Schrijver CM, Schrijver LK, Postema K, van Netten JJ. Mechanical Noise Improves the Vibration Perception Threshold of the Foot in People With Diabetic Neuropathy. J Diabetes Sci Technol 2020; 14:16-21. [PMID: 30328708 PMCID: PMC7189161 DOI: 10.1177/1932296818804552] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
BACKGROUND Mechanical noise may improve somatosensation at the dorsal side of the foot, but the effect at the plantar side of the foot, the side most at risk for foot ulceration, is unknown. Moreover, techniques used in research so far have several problems that limit applicability in daily practice. Piezoelectric actuators may provide mechanical noise with better clinical applicability. We assessed the effects of piezoelectric actuators generating mechanical noise on the vibration perception threshold (VPT) at the plantar side of the foot in people with diabetic neuropathy. METHODS Double-blind within-subjects design in a controlled laboratory setting including participants with diabetic neuropathy (N = 40; 18 male; mean age 69.6 years; mean duration of diabetes 14.1 years; mean BMI 30.5). VPT was measured at three plantar foot locations with and without mechanical noise applied via piezoelectric actuators. RESULTS Mechanical noise improved VPT at metatarsophalangeal joint (MTP) 1 (left 39.3V vs 43.5V; right 39.0 vs 42.6 V), MTP5 (left 37.5V vs 41.7V; right 34.5V vs 40.8V) and the heel (left 40.0V vs 44.0V; right 39.3V vs 41.0V), all P < .001. CONCLUSIONS Mechanical noise improves VPT at the plantar side of the foot in people with diabetic neuropathy. This is an important step for further development of insoles using mechanical noise that may have the potential to improve VPT and decrease the risk of foot ulceration.
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Affiliation(s)
- Jennefer B. J. Zwaferink
- Ziekenhuisgroep Twente, Almelo and
Hengelo, The Netherlands
- Amsterdam UMC, Department of
Rehablitation Medicine, University of Amsterdam, Amsterdam Movement Sciences, The
Netherlands
- Jennefer B. J. Zwaferink, Department of
Rehabilitation Medicine, Amsterdam UMC, University of Amsterdam, Amsterdam
Movement Sciences, Meibergdreef 9, Amsterdam, 1105 AZ, The Netherlands.
| | - Juha M. Hijmans
- Department of Rehabilitation Medicine,
University of Groningen, University Medical Center Groningen, The Netherlands
| | | | | | - Klaas Postema
- Department of Rehabilitation Medicine,
University of Groningen, University Medical Center Groningen, The Netherlands
| | - Jaap J. van Netten
- Ziekenhuisgroep Twente, Almelo and
Hengelo, The Netherlands
- Amsterdam UMC, Department of
Rehablitation Medicine, University of Amsterdam, Amsterdam Movement Sciences, The
Netherlands
- School of Clinical Sciences, Queensland
University of Technology, Brisbane, Australia
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Porto C, Lemos T, Ferreira AS. Analysis of the postural stabilization in the upright stance using optimization properties. Biomed Signal Process Control 2019. [DOI: 10.1016/j.bspc.2019.04.009] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
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The effects of sub-threshold vibratory noise on visuomotor entrainment during human walking and standing in a virtual reality environment. Hum Mov Sci 2019; 66:587-599. [PMID: 31255870 PMCID: PMC6934930 DOI: 10.1016/j.humov.2019.06.009] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2019] [Revised: 06/13/2019] [Accepted: 06/14/2019] [Indexed: 01/25/2023]
Abstract
Humans will naturally synchronize their posture to the motion of a visual surround, but it is unclear if this visuomotor entrainment can be attenuated with an increased sensitivity to somatosensory information. Sub-threshold vibratory noise applied to the Achilles tendons has proven to enhance ankle proprioception through the phenomenon of stochastic resonance. Our purpose was to compare visuomotor entrainment during walking and standing, and to understand how this entrainment might be attenuated by applying sub-threshold vibratory noise over the Achilles tendons. We induced visuomotor entrainment during standing and treadmill walking for ten subjects (24.5 ± 2.9 years) using a speed-matched virtual hallway with continuous mediolateral perturbations at three different frequencies. Vibrotactile motors over the Achilles tendons provided noise (0-400 Hz) with an amplitude set to 90% of each participant's sensory threshold. Mediolateral sacrum, C7, and head motion was greatly amplified (4-8× on average) at the perturbation frequencies during walking, but was much less pronounced during standing. During walking, individuals with greater mediolateral head motion at the fastest perturbation frequency saw the greatest attenuation of that motion with applied noise. Similarly, during standing, individuals who exhibited greater postural sway (as measured by the center of pressure) also saw the greatest reductions in sway with sub-threshold noise applied in three of our summary metrics. Our results suggest that, at least for healthy young adults, sub-threshold vibratory noise over the Achilles tendons can slightly improve postural control during disruptive mediolateral visual perturbations, but the applied noise does not substantially attenuate visuomotor entrainment during walking or standing.
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White O, Babič J, Trenado C, Johannsen L, Goswami N. The Promise of Stochastic Resonance in Falls Prevention. Front Physiol 2019; 9:1865. [PMID: 30745883 PMCID: PMC6360177 DOI: 10.3389/fphys.2018.01865] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2018] [Accepted: 12/11/2018] [Indexed: 12/13/2022] Open
Abstract
Multisensory integration is essential for maintenance of motor and cognitive abilities, thereby ensuring normal function and personal autonomy. Balance control is challenged during senescence or in motor disorders, leading to potential falls. Increased uncertainty in sensory signals is caused by a number of factors including noise, defined as a random and persistent disturbance that reduces the clarity of information. Counter-intuitively, noise can be beneficial in some conditions. Stochastic resonance is a mechanism whereby a particular level of noise actually enhances the response of non-linear systems to weak sensory signals. Here we review the effects of stochastic resonance on sensory modalities and systems directly involved in balance control. We highlight its potential for improving sensorimotor performance as well as cognitive and autonomic functions. These promising results demonstrate that stochastic resonance represents a flexible and non-invasive technique that can be applied to different modalities simultaneously. Finally we point out its benefits for a variety of scenarios including in ambulant elderly, skilled movements, sports and to patients with sensorimotor or autonomic dysfunctions.
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Affiliation(s)
- Olivier White
- INSERM UMR1093-CAPS, Université Bourgogne Franche-Comté, UFR des Sciences du Sport, Dijon, France.,Acquired Brain Injury Rehabilitation, Faculty of Medicine and Health Sciences, School of Health Sciences, University of East Anglia, Norwich Research Park, Norwich, United Kingdom
| | - Jan Babič
- Laboratory for Neuromechanics and Biorobotics, Jožef Stefan Institute, Ljubljana, Slovenia
| | - Carlos Trenado
- Leibniz Research Centre for Working Environment and Human Factors TU Dortmund (ifADO), Institute of Clinical Neuroscience and Medical Psychology, University Hospital Düsseldorf, Düsseldorf, Germany
| | - Leif Johannsen
- Acquired Brain Injury Rehabilitation, Faculty of Medicine and Health Sciences, School of Health Sciences, University of East Anglia, Norwich Research Park, Norwich, United Kingdom
| | - Nandu Goswami
- Otto Loewi Research Center for Vascular Biology, Immunology and Inflammation, Medical University of Graz, Graz, Austria
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Ross J, Will O, McGann Z, Balasubramaniam R. Auditory white noise reduces age-related fluctuations in balance. Neurosci Lett 2016; 630:216-221. [DOI: 10.1016/j.neulet.2016.07.060] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2016] [Revised: 07/21/2016] [Accepted: 07/29/2016] [Indexed: 11/15/2022]
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10
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Borel L, Ribot-Ciscar E. Improving postural control by applying mechanical noise to ankle muscle tendons. Exp Brain Res 2016; 234:2305-14. [PMID: 27021075 DOI: 10.1007/s00221-016-4636-2] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2015] [Accepted: 03/18/2016] [Indexed: 10/22/2022]
Abstract
The application of subthreshold mechanical vibrations with random frequencies (white mechanical noise) to ankle muscle tendons is known to increase muscle proprioceptive information and to improve the detection of ankle movements. The aim of the present study was to analyze the effect of this mechanical noise on postural control, its possible modulation according to the sensory strategies used for postural control, and the consequences of increasing postural difficulty. The upright stance of 20 healthy young participants tested with their eyes closed was analyzed during the application of four different levels of noise and compared to that in the absence of noise (control) in three conditions: static, static on foam, and dynamic (sinusoidal translation). The quiet standing condition was conducted with the eyes open and closed to determine the subjects' visual dependency to maintain postural stability. Postural performance was assessed using posturographic and motion analysis evaluations. The results in the static condition showed that the spectral power density of body sway significantly decreased with an optimal level of noise and that the higher the spectral power density without noise, the greater the noise effect, irrespective of visual dependency. Finally, noise application was ineffective in the foam and dynamic conditions. We conclude that the application of mechanical noise to ankle muscle tendons is a means to improve quiet standing only. These results suggest that mechanical noise stimulation may be more effective in more impaired populations.
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Affiliation(s)
- Liliane Borel
- Aix-Marseille Université, CNRS, NIA UMR 7260, Case B, Centre Saint-Charles, Place Victor Hugo, 13331, Marseille Cedex 03, France.
| | - Edith Ribot-Ciscar
- Aix-Marseille Université, CNRS, NIA UMR 7260, Case B, Centre Saint-Charles, Place Victor Hugo, 13331, Marseille Cedex 03, France
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Abney DH, Kello CT, Warlaumont AS. Production and Convergence of Multiscale Clustering in Speech. ECOLOGICAL PSYCHOLOGY 2015. [DOI: 10.1080/10407413.2015.1068653] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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Eddy CL, Kelty-Stephen DG. Nesting of Focal Within Peripheral Vision Promotes Interactions Across Nested Time Scales in Head Sway: Multifractal Evidence From Accelerometry During Manual and Walking-Based Fitts Tasks. ECOLOGICAL PSYCHOLOGY 2015. [DOI: 10.1080/10407413.2015.991663] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
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Bell IR. Nonlinear effects of nanoparticles: biological variability from hormetic doses, small particle sizes, and dynamic adaptive interactions. Dose Response 2014; 12:202-32. [PMID: 24910581 PMCID: PMC4036395 DOI: 10.2203/dose-response.13-025.bell] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Researchers are increasingly focused on the nanoscale level of organization where biological processes take place in living systems. Nanoparticles (NPs, e.g., 1-100 nm diameter) are small forms of natural or manufactured source material whose properties differ markedly from those of the respective bulk forms of the "same" material. Certain NPs have diagnostic and therapeutic uses; some NPs exhibit low-dose toxicity; other NPs show ability to stimulate low-dose adaptive responses (hormesis). Beyond dose, size, shape, and surface charge variations of NPs evoke nonlinear responses in complex adaptive systems. NPs acquire unique size-dependent biological, chemical, thermal, optical, electromagnetic, and atom-like quantum properties. Nanoparticles exhibit high surface adsorptive capacity for other substances, enhanced bioavailability, and ability to cross otherwise impermeable cell membranes including the blood-brain barrier. With super-potent effects, nano-forms can evoke cellular stress responses or therapeutic effects not only at lower doses than their bulk forms, but also for longer periods of time. Interactions of initial effects and compensatory systemic responses can alter the impact of NPs over time. Taken together, the data suggest the need to downshift the dose-response curve of NPs from that for bulk forms in order to identify the necessarily decreased no-observed-adverse-effect-level and hormetic dose range for nanoparticles.
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